Waveguide switch



2,997,670 WAVEGUIDE SWITCH Georges Pircher, Paris, and Michel R. Y. Chaussedoux,

Montrouge, France, assignors to Cie Francaise Thomson-Houston, Paris, France Filed Dec. 24, 1958, Ser. No. 782,909 Claims priority, application France Dec. 27, 1957 3 Claims. (Cl. 333--7) This invention relates to a waveguide switch and particularly to a waveguide switch which makes it possible to join four channels by twos in two different ways.

Known devices of this kind have a common drawback. If the switching element is operated, the impedance of the devices as seen from one of their branches undergoes considerable changes. This has particularly the result that, if one of the branches is connected to an emitter, it must stop functioning during the switching operation. Furthermore, most waveguide switches "heretofore known give no possibility to establish a satisfactory bypass between channels which are not joined.

It is therefore an obpect of this invention to provide an improved waveguide switch.

It is a further object of this invention to permit the switching of waves while such waves are being propagated through waveguides.

It is an object of this invention to provide high speed switching of guided waves.

One waveguide switch embodiment of this invention, free of the above mentioned drawbacks, comprises a per forated, wave reflecting, movable tape which is passed through a pair of waveguides interconnected by short slot hybrid couplers in a manner to change the normal wave coupling action established by the couplers.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIGS 1 and 2 show schematic waveguide structures useful in explaining the principles of the present invention;

FIG. 3 is a first embodiment of the invention; and

FIG. 4 illustrates a further embodiment of the invention.

Referring to FIG. 1, there is shown a waveguide structure using the properties of a set of two series connected guide couplers of the type known as 3 db. It is known that this is the designation for directional couplers which, between the output branches, cause the equal partition of the incident energy in an input branch. As may be seen in FIG. 1, couplers 1 and 2 establish communication between guides 3 and 4, of which the ends are joined to channels a, b, and c, d respectively (not shown). The essential property of this set should be mentioned here. If a wave enters branch :1 all energy connected with this wave is transmitted to branch d, whereas no energy at all enterse branch b. Likewise, a wave sent into branch is transmitted into branch b.

A waveguide switch as per the invention consists of a set of 3 db couplers as described above, as well as of means to introduce simultaneously into each guide, between the couplers, a reflector or vane (5 or 6, FIG. 2) which establishes a short circuit. The introduction of reflectors into guides 3 and 4 suppresses any communication between channels a and d on one hand and channels c and b on the other, whereas it establishes the connection between the adjoining channels a, c, and b, d.

For the better understanding of the technical characteratent istics of the invention two examples of its realization are described and shown in FIGS. 3 and 4, but it must be understood that these limit in no way the scope of the invention either as to its realization or as to its application.

Examination of FIGS. 3 and 4 shows that guides 3 and 4 diverge between the couplers 1 and 2. In accordance with the invention this arrangement is preferable because it makes it possible to introduce the wave reflectors into each guide in the same manner. These reflectors can be actuated by identical movements when a switch is operated. In the case of the arrangement as per FIG. 3, the communications between couplers 1 and 2 are established or suppressed by the movement of a wave reflecting perforated band 7 which crosses the two guides vertically to their axes. Evidently the distance between the perforations or windows 8, 3 of the band must be the same as the distance I between the guides.

The realization shown in the last figure makes it possible to obtain a better decoupling between the channels a, d and b, c when the communications between couplers 1 and 2 are suppressed.

For this purpose two reflectors are introduced into the guides 1 and 2. An endless metal tape 10 carried by two identical pulleys 11 and 12 is used. Windows 13, 14, 15 and 16 are punched out in tape 10. The distance between windows 13, 14 as well as that between windows 15 and 16 are punched in tape 10. The distance between the windows 13 and 14 as well as that between windows 15 and 16 is equal to distance 1 between the guides. The positions of the perforations on the tape are evidently determined so that the windows 13, 15 and 14, 16 can be brought to face each other in the guide. The distance between the tapes and consequently the diameter of the pulleys must be substantially the length of the wave being propagated in guides 3 and 4. The obstacle formed by the two parts of the tape which encloses a section of the guide between them is thus anti-resonant. It follows that this improves the decoupling between channels a and d (or b and c), since the tape in principle suppresses communication between cou-plers 1 and 2.

The openings of the guides 3 and 4, through which the tape enters and leaves the guides, are provided with radio frequency chokes 17, 18, .18 and 20 which confine the propagation of the radio frequency waves to the waveguides.

A switch as just described may serve to connect a1- ternately an emitter to two antennas. It can also be used to connect an emitter to an antenna or to a terminal device with the same impedance which can dissipate an adequate power. All required controls and tests can be made by the emitter without radiating energy to the outside. This switch is of particular value when used to connect the emiter and the antenna of a radio detection system. The presence of the latter is not revealed through the control and test operations.

In the case of such utilization i-f branch 0 of the switch is connected to the wave emitter 21 and branch I) to the antenna 22, whereas branches a and d are connected respectively to terminal devices 23 and 24 without reflection, that provided in a is able to dissipate the power of the wave produced by the emitter.

Referring to FIG. 4, the invention has particular application to an arrangement where separate sources of waves are located at 21 and 24. When the tape is in the wave coupling position, that is, the openings in the tape appear in the spaced apart guide portions, waves from source 21 are coupled to a load 22 and waves from source 24 are coupled to a load 23. As the tape is moved such that the wave reflecting portions thereof pass across the guides, the waves from source 21 are switched to load a and the waves from source d are switched to load 22. In certain applications, there may be a difference in frequency between the waves from sources 21 and 24. In this case the spacing between the parallel tapes would be dimensioned to be a quarter Wavelength long at the mean operating frequency.

The applicant has designed a switch of the type shown in FIG. 4. The standing wave ratio in the guides 3 and 4 was lower than 1.1 in a frequency band having a width of if F is the central operating frequency and when the tape obstructs the guides 3 and 4 the decoupling between channels a and d as well as between channels b and c amounts to 80 db.

While a specific embodiment has been shown and described, it will of course be understood that various modifications may yet be devised by those skilled in the art which will embody the principles of the invention and found in the true spirit and scope thereof.

What I claim and desire to secure by Letters Patent of the United States is:

l. A first and second waveguide, a pair of spaced apart slot hybrid couplers interconnecting said waveguides, portions of said waveguides between said slot hybrid couplers being spaced apart, a pair of wave reflecting tapes each having a pair of openings, each of said openings being substantially equal to the inside dimensions of said waveguide portions, means for simultaneously moving said tapes in opposite directions along parallel paths through said portions of waveguide and substantially perpendicular to the longitudinal axes thereof, the tapes being spaced apart a quarter wavelength at the operating frequency of the waveguide P rtions and the distance between the openings of each tape being equal to the distance between said portions of waveguide.

2. A first and second waveguide, a pair of spaced apart slot hybrid couplers interconnecting said waveguides, portions of said waveguides between said slot hybrid couplers being spaced apart, means for suppressing or establishing wave propagation between said couplers comprising an endless loop wave reflecting tape having four wave coupling openings, and means for selectively and synchronously introducing the wave reflecting portions or the wave coupling portions of said tape into said waveguide portions in directions substantially perpendicular to the longitudinal axes thereof and in pairs spaced apart a quarter wavelength at the mean operating frequency of said waveguides.

3. A firs-t and second waveguide, a pair of spaced apart slot hybrid couplers interconnecting said waveguides, portions of said waveguides between said hybrid couplers being spaced apart, means for establishing or suppressing wave propagation betwen said couplers comprising an endless loop of wave reflecting tape having four wave coupling openings, and means for moving said tape through said portions of waveguide such that said openings pass into and out of wave coupling relationship with said waveguides in a direction substantially perpendicular to the longitudinal axes thereof, the distance between said openings being the same as the distance between said portions of waveguide.

References Cited in the file of this patent UNITED STATES PATENTS 2,586,993 Riblet Feb. 26, 1952 2,709,241 Riblet May 24, 1955 2,869,081 Teeter Jan. 13, 1959 

